#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Wed Oct  6 14:16:43 2021

@author: 
"""


class Car:
    def __init__(self, length, width):
        # l↓
        # + - - +←w
        # |     |
        # |     |
        # |     |
        # +- - -+
        self.length = length
        self.width = width

    def add_axle(self, at_length):
        """添加轮轴，轮子必须安装在轮子的一端。
        """  # TODO

    def add_wheel(self, axle, MLobject):
        """
        """  # TODO
        ...
        MLobject.add_car(self, ...)

    def wheel_speed(self, wheel, new_speed):
        """供轮子调用
        """  # TODO
